Funds are requested to purchase a new laser desorption mass spectrometer (LDMS) for the UCLA Pasarow Mass Spectrometry Laboratory. This is a shared facility jointly supported by the Department of Chemistry and Biochemistry (College of Letters and Sciences) and the Department of Psychiatry and Biobehavioral Sciences (School of Medicine) that is available to the entire UCLA campus research and teaching enterprise. The facility currently has one LDMS system. This is a PerSeptive Biosystems Voyager RP instrument which is the only LDMS on the UCLA campus. The work load for this instrument has grown since its acquisition in October 1994 such that instrument time is heavily booked. More importantly, this instrument has modest resolving and mass accuracy capabilities because it does not have the delayed ion extraction option. The absence of delayed ion extraction severely limits the usefulness of this instrument, particularly in the emerging proteome era when an increasing number of research groups need accurate mass assignments for protein and peptide identification and optimal resolution for the direct analysis of complex mixtures without having to resort to chromatography, and in the field of organic polymers where accurate mass measurements above 1,000 Daltons are becoming increasingly important. These capabilities are crucial for the continued productivity, success and competitiveness of several campus research programs in the biological and chemical sciences. Reflecting this diversity of use, descriptions of the research of the major users of LDMS are provided. In addition to the role it plays in these research programs, the facility handles numerous routine LDMS analyses, further substantiating the importance of this new instrument to this campus.